Impact scores of invasive plants are biased by disregard of environmental co-variation and non-linearity

Prioritisation of high-impact species is becoming increasingly important for management of introduced species (‘neobiota’) because of their growing number of which, however, only a small fraction has substantial impacts. Impact scores for prioritising species may be affected by the type of effect model used. Recent studies have shown that environmental co-variation and non-linearity may be significant for effect models of biological invasions. Here, we test for differences in impact scores between simple and complex effect models of three invasive plant species (Heracleum mantegazzianum, Lupinus polyphyllus, Rosa rugosa). We investigated the effects of cover percentages of the invasive plants on species richness of invaded communities using both simple linear effect models (‘basic models’) and more complex linear or nonlinear models including environmental co-factors (‘full models’). Then, we calculated impact scores for each invasive species as the average reduction of species richness predicted by basic and full effect models. All three non-native species had negative effects on species richness, but the full effect models also indicated significant influence of habitat types. Heracleum mantegazzianum had uniform linear effects in all habitats, while effects of L. polyphyllus interacted strongly with habitat type, and R. rugosa showed a marked non-linear relationship. Impact scores were overestimated by basic effect models for H. mantegazzianum and R. rugosa due to disregard of habitat effects and non-linearity, respectively. In contrast, impact of L. polyphyllus was underestimated by the basic model that did not account for the strong interaction of invader cover and habitat type. We conclude that simple linear models will often yield inaccurate impact scores of non-native species. Hence, effect models should consider environmental co-variation and, if necessary, non-linearity of the effects of biological invasions on native ecosystems

Edges effects on seed predation by rodents in deciduous forests of northern Switzerland

Seed predation by rodents affects plant population dynamics and it mayrespond to changes in vegetation structure at forest edges. This studyinvestigates the magnitude and direction of a potential edge effect intemperatedeciduous forests, and it seeks possible explanations based on predatorabundance and vegetation structure. The study was conducted at twelve forestedges in northern Switzerland; in six sites all shrubs at the forest edge wereremoved, whereas the other sites maintained a structurally rich shrub layer. Ineach site three transects were laid out from the edge towards the forestinterior. In six plots along these transects (at 1, 3, 6, 12, 25, 50m) we studied seed removal from experimental dishes, rodentabundance in live-traps and four characteristics of the vegetation structure.For both woody seed species (Prunus avium,Viburnum lantana) predation was significantly higher nearthe forest edge in the structurally rich sites; in the other sites no suchgradient was found. Selectively accessible dishes revealed that rodents werethemain predators, whereas predation by insects or molluscs was not observed.Abundance of rodents (Apodemus flavicollis, A.sylvaticus, Clethrionomys glareolus) washighestunder dense shrubs close to the forest edge. In the structurally rich sitesthere was a clear gradient of decreasing shrub cover from the edge towards theforest interior; a weaker gradient was observed in the structurally poor sites.We conclude that high shrub cover near the forest edge is the main determinantfor edge effects in seed predation, and edges without a shrub belt show no sucheffec

Gewinnung von Basissaatgut für die produktionsintegrierte Förderung seltener und gefährdeter Ackerwildkräuter

Re-introduction and integrated conservation of rare arable plants is one approach to restore agro-biodiversity. Our study investigated occurrence and population size of rare arable plant species on 94 fields in Bavaria. 50 threatened species could be found with populations >100 individuals. This enabled an initial collection of seeds which will be propagated and sown in extensively managed fields

Timing of Arrival and Native Biomass Are Better Proxies of Invasion Suppression in Grassland Communities

A challenge in many restoration projects, in particular when establishing de novo communities, is the arrival and later dominance of invasive alien plants. This could potentially be avoided by designing invasion-resistant native communities. Several studies suggest achieving this by maximizing trait similarity between natives and potential invaders (“limiting similarity”), but evidence supporting this approach is mixed so far. Others pose that the relative time of arrival by native and invasive species (“priority effects”) could play a stronger role, yet this factor and its interaction with trait similarity is not fully understood in the context of ecological restoration. Thus, we hypothesized that multi-trait similarity would increase suppression of invasive species by native communities, and that the effect would be stronger when natives arrive first. We established two distinct communities of native central European grassland species based on native–invasive trait similarity, and then tested the introduction of invasive Ambrosia artemisiifolia and Solidago gigantea separately when arriving in the native communities at two times, i.e., sown either at the same time as the natives or 2 weeks after. For the traits selected, our data did not provide evidence for a limiting similarity effect, but rather supported priority effects. Both native communities more effectively suppressed invaders that arrived after the natives. In addition, the native community that produced the most biomass suppressed both invasive species more than the most ecologically similar community. This effect of biomass revealed that prioritizing native–invader ecological similarity can fail to account for other community characteristics that affect invasion resistance, such as biomass. Instead, native communities could be designed to enhance priority effects through the inclusion of early and fast developing species. We conclude that native community composition plays a significant role in the establishment success by invasive species, and resource pre-emption seems more significant than trait similarity. In terms of grassland restoration, native species should be selected based on plant traits related to fast emergence and early competitiveness

Wiederansiedlung seltener und gefährdeter Ackerwildpflanzen auf Ökobetrieben. Teilprojekt Freising: Einfluss von Feldfrucht und Aussaatzeitpunkt

Intensive land use has led to a drastic decline of arable weeds in Central Europe. The objective of the project “Restoration of local populations of rare and endangered arable field plants on organic farms in Germany” is to develop methods for a successful re-establishment of arable weeds on fields where absence of herbicides provides favourable development conditions. Two complementary approaches are tested by research teams at Freising and Witzenhausen. In Freising two exact trials were set up in order to find suitable crops and dates for the initial sowing of three rare and endangered species (Consolida regalis, Legousia speculum-veneris, Lithospermum arvense). The study area is located in the Munich Plain which is characterized by limestone gravel. First results show a better establishment of all three species on plots with a reduced sowing density of the crop. Furthermore, sowing in early autumn seems to be beneficial for the establishment of the study species

Low precipitation due to climate change consistently reduces multifunctionality of urban grasslands in mesocosms

Urban grasslands are crucial for biodiversity and ecosystem services in cities, while little is known about their multifunctionality under climate change. Thus, we investigated the effects of simulated climate change, i.e., increased [CO2] and temperature, and reduced precipitation, on individual functions and overall multifunctionality in mesocosm grasslands sown with forbs and grasses in four different proportions aiming at mimicking road verge grassland patches. Climate change scenarios RCP2.6 (control) and RCP8.5 (worst-case) were simulated in walk-in climate chambers of an ecotron facility, and watering was manipulated for normal vs. reduced precipitation. We measured eight indicator variables of ecosystem functions based on below- and aboveground characteristics. The young grassland communities responded to higher [CO2] and warmer conditions with increased vegetation cover, height, flower production, and soil respiration. Lower precipitation affected carbon cycling in the ecosystem by reducing biomass production and soil respiration. In turn, the water regulation capacity of the grasslands depended on precipitation interacting with climate change scenario, given the enhanced water efficiency resulting from increased [CO2] under RCP8.5. Multifunctionality was negatively affected by reduced precipitation, especially under RCP2.6. Trade-offs arose among single functions that performed best in either grass- or forb-dominated grasslands. Grasslands with an even ratio of plant functional types coped better with climate change and thus are good options for increasing the benefits of urban green infrastructure. Overall, the study provides experimental evidence of the effects of climate change on the functionality of urban ecosystems. Designing the composition of urban grasslands based on ecological theory may increase their resilience to global change.publishedVersio

Exponential signaling gain at the receptor level enhances signal-to-noise ratio in bacterial chemotaxis

Peer reviewedPublisher PD

Phylogenetic distance controls plant growth during early restoration of a semi-arid riparian forest

1. Little attention has been paid to phylogenetic diversity during restoration initiatives. Because plant phylogenetic distance can be a surrogate for functional diversity, its consideration could foster the restoration of degraded areas. 2. This study investigates the influence of species richness and phylogenetic relatedness during early restoration of a riparian forest located between the Atlantic Forest and semi-arid ecosystems in NE Brazil. The restoration experiment was established along a perennial stream in Monte Alegre, RN, investigating the significance of species richness and phylogenetic diversity for sapling survival and growth of the restored communities. 3. We used phylogenetic information on 47 tree species naturally occurring at the study site. The resulting phylogenetic tree had a basal node with three major clades. To implement the experiment, three species from each clade were randomly selected, resulting in nine species (from five families). We defined five levels of diversity: (i) no planting, (ii) monoculture, (iii) three phylogenetically related species (same clade), (iv) three phylogenetically distant species (different clades) and (v) nine species. The experiment consisted of 96 (12 m × 10 m) plots established along the two margins of the stream. Overall, 1656 saplings (20–50 cm) were planted in September 2015 (184 per species). We tested whether the survival and growth of saplings are influenced by the number of species planted and phylogenetic distance among them. 4. We assessed plant mortality and growth during two consecutive years (2016 and 2017). Survival was lower but relative growth was higher for plants near the stream. After controlling for differences in initial size, plots with phylogenetically distant species produced significantly taller plants, but only when occurring near the stream. Diversity treatments did not influence plant survival, while initial size determined plant survival and growth. 5. Our findings show that greater phylogenetic distance led to increased plant growth, probably, because of the presence of functionally divergent species that use resources in a complementary way. Therefore, plant phylogenetic relatedness should be considered during the design of restored communities to improve the outcomes of future restoration initiatives.Phylogenetic distance controls plant growth during early restoration of a semi-arid riparian forestpublishedVersio